TABLE OF CONTENTS Almost all measuring instruments provide the user with a quantitative measurement. The user always expects a known level of confidence in that measured value. The ultimate aim of a measurement is to have accuracy, reliability and confidence in the exercise of measurement and its quantitative output.
Calibration is the process that ensures accuracy in a measurement, and makes the measurement and its process traceable to standards discussed in chapter 1. With the growing adoption of quality standards such as ISO9000, many institutes are paying more attention to calibration of instruments, because all measurements have a direct bearing on product quality or service quality.
Since the end of World War II, technical advances have permited scientists to reduce uncertainty in measurements dramatically. In the 1940s, working measurements were made with an analogue iron-vane or D'Arsonval meter. With care, uncertainties were in the range of 0.5 per cent of full scale, or 5000 p.p.m. As shown in Figure 15.1, that 5000 p.p.m. in the 1940s became 100 p.p.m. by 1960, 10 p.p.m. by 1970 and 2 p.p.m. today [1].
This chapter provides an introduction to calibration of common instruments and the calibrators.
Simply stated, metrology is the science of measurement. Everything that has to do with measurement, be it designing, conducting, or analysing the results of a test, exists within the realm of metrology. These things cover the range from the abstract, comparing...
